IgG Anti-Rh(D) is currently used for prevention of the Rh alloimmunization of blood group Rh negative women. The demand of this product is increasing due to a new indication at 28-30 weeks of pregnancy along with an increase in the population at risk. Conversely, the source for the elaboration of the IgG anti-Rh (plasma from immunized Rh negative people), carries important pathogenic risks, and is also used for preparation of blood typing reagents. Therefore, it is of interest to produce human recombinant IgG1, IgG3 and IgM antibodies specific for the Rh(D) blood group antigen. To do that Recombinant DNA techniques developed in the laboratory of Dr. S.L. Morrison (UCLA-USA) will be applied to clone the variable region from anti-Rh antibodies, using as starting material antigen-specific human-mouse heterohybridomas produced in our laboratory (Montano and Romano, IVIC-Venezuela). The V(H) region will be expressed in association with human gamma 1, gamma 3, or mu constant regions; the V(L) region will be joined to the constant region of the human kappa light chain. Recombinant IgG1 and IgG3 anti-Rh are expected to be useful in designing a prophylactic material for the prevention of maternal Rh alloimmunization. Recombinant IgM anti-Rh must serve for the elaboration of a commercial reagent useful in Rh blood typing.